Synthesis of hydrogels made of poly-γ-glutamic acid (γ-PGA) for potential applications as probiotic-delivery vehicles

© 2020 The Authors. Published by MDPI. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.3390/app10082787Numerous hydrogels made of poly-γ-glutamic acid (γ-PGA) and various cross-linkers have been explored, but only limited data on hydrogels made of γ-PGA and poly(ethylene glycol) (PEG) are available. In this study, γ-PGA, a biodegradable and edible biopolyamide, was successfully cross-linked with selected PEGs to obtain a series of hydrogels. The swelling behaviour of these hydrogels was investigated under various pH conditions. It was also found that the structure of the cross-linker (linear or branched) affected the hydrogels’ swelling behaviour. In addition, in disc diffusion assay, hydrogel discs loaded with antibiotic were tested against Staphylococcus aureus and Escherichia coli. Prolonged activity of hydrogels loaded with antibiotics in comparison to paper discs containing antibiotics was observed. Moreover, the protective effect of hydrogels on entrapped probiotic cells subjected to low pH was investigated. The hydrogel swelling ratio and amount influenced the survival rate of the protected bacteria. Considering potential biomedical applications of hydrogels, cytotoxicity was evaluated towards two cell lines, MSTO and PANC 1

Bioconversion of plastic waste based on mass full carbon backbone polymeric materials to value-added polyhydroxyalkanoates (PHAs)

© 2022 The Authors. Published by MDPI. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.3390/bioengineering9090432This review article will discuss the ways in which various polymeric materials, such as polyethylene (PE), polypropylene (PP), polystyrene (PS), and poly(ethylene terephthalate) (PET) can potentially be used to produce bioplastics, such as polyhydroxyalkanoates (PHAs) through microbial cultivation. We will present up-to-date information regarding notable microbial strains that are actively used in the biodegradation of polyolefins. We will also review some of the metabolic pathways involved in the process of plastic depolymerization and discuss challenges relevant to the valorization of plastic waste. The aim of this review is also to showcase the importance of methods, including oxidative degradation and microbial-based processes, that are currently being used in the fields of microbiology and biotechnology to limit the environmental burden of waste plastics. It is our hope that this article will contribute to the concept of bio-upcycling plastic waste to value-added products via microbial routes for a more sustainable future.This research was funded by the University of Wolverhampton Research Investment Fund (RIF4), the ERDF Science in Industry Research Centre (SIRC 01R19P03464) project, and the Schlumberger Foundation Faculty for the Future Fellowship. Additionally, partial support was provided by the European Regional Development Fund Project via EnTRESS No 01R16P00718 and the PELARGODONTProjectUM0-2016/22/Z/STS/00692financedundertheM-ERA.NET2Program of Horizon 2020.Published versio

Bioactive and functional oligomers derived from natural PHA and their synthetic analogs

This is an accepted manuscript of a chapter published by CRC Press in The Handbook of Polyhydroxyalkanoates Postsynthetic Treatment, Processing and Application on 05/11/2020, available online: https://www.taylorfrancis.com/books/e/9781003087663/chapters/10.1201/9781003087663-5 The accepted version of the publication may differ from the final published version.Polyhydroxyalkanoate oligomers (oligo-PHA) are low molar mass PHA consisting of a small number of 3-hydroxyacid repeat units (usually not more than 200 residue units). They can be synthesized either naturally in eukaryotic cells and in prokaryotic cells through intracellular or extracellular degradation of storage PHA to yield natural oligomers, or via several chemical modifications such as basic hydrolysis or transesterification. The synthetic analogs of natural PHA oligomers are obtained by anionic ring-opening polymerization (ROP) of β-substituted β-lactones. These synthetic and biodegradable oligomers, through various chemical modifications, can further allow the preparation of bioactive oligomers with attractive properties for novel and high value-added applications, especially in medicine, agrochemistry, and cosmetology. Bioactive oligomers are also biodegradable: they possess enhanced properties, controlled functional end groups, and thus can be potential components of copolymers or blends with other biodegradable polymers. The natural and synthetic routes used for the preparation of selected bioactive PHA oligomers and their detailed characterization by mass spectrometry are discussed in this chapter

Environmental cleaning mission Bioconversion of oxidatively fragmented polyethylene plastic waste to value-added copolyesters

The innovative recycling method, we are proposing, relies upon the controlled oxidative fragmentation of waste LDPE plastic to the inexpensive substrates for future sustainable production of PHAs with the aid of Cupriavidus necator. LDPE oxidized fragments (PE-F) were obtained from the re-engineering LDPE film by means of pro-oxidant/pro-degradant additives, followed by treatment under natural UV light. Cupriavidus necator was grown in either tryptone soya broth (TSB) or basal salt medium (BSM) supplemented with PE-F for 48 h. PHA production was higher in TSB supplemented with PE-F (29%) than in TSB alone (only 0.6%). No PHA was detected in either BSM alone or BSM supplemented with PE-F. The recovered PHA was characterized using GPC, NMR, and electrospray ionization tandem mass spectrometry (ESI-MS/MS). These analytical tools applied confirmed that the resulting PHA was a terpolymer having an average molar mass of 624 kg/mol and consisting of 3-hydroxybutyrate (HB), 3-hydroxyvalerates (HV) and 3-hydroxyhexanoate (HH) co-monomer units randomly distributed along the chain backbone

Mass spectrometry reveals molecular structure of polyhydroxyalkanoates attained by bioconversion of oxidized polypropylene waste fragments

This study investigated the molecular structure of the polyhydroxyalkanoate (PHA) produced via a microbiological shake flask experiment utilizing oxidized polypropylene (PP) waste as an additional carbon source. The bacterial strain Cupriavidus necator H16 was selected as it is non-pathogenic, genetically stable, robust, and one of the best known producers of PHA. Making use of PHA oligomers, formed by controlled moderate-temperature degradation induced by carboxylate moieties, by examination of both the parent and fragmentation ions, the ESI-MS/MS analysis revealed the 3-hydroxybutyrate and randomly distributed 3-hydroxyvalerate as well as 3-hydroxyhexanoate repeat units. Thus, the bioconversion of PP solid waste to a value-added product such as PHA tert-polymer was demonstrated.This research was funded by the Research Investment Fund, University of Wolverhampton, Faculty of Science and Engineering, UK. This work was also partially supported the European Regional Development Fund Project EnTRESS No 01R16P00718 and the PELARGODONT Project UM0-2016/22/Z/STS/00692 financed under the M-ERA.NET 2 Program of Horizon 2020.Published onlin